1. Field of the Invention
The present invention relates to a vibration isolation table for supporting an object to be isolated from vibration such as a precision instrument while isolating the object from vibration which is transmitted from the floor to the vibration isolation table, and more specifically relates to such a vibration isolation table, the natural vibration frequency of which in the horizontal direction is small.
2. Description of the Related Art
As an example of a vibration isolation table for preventing vibration from the floor from being transmitted to a precision instrument (e.g., an optical stepper or an electron microscope) which is supported by the vibration isolation table, a vibration isolation table wherein a bellows is fixed to an upper part of a stationary housing, a mount on which a precision instrument is mounted is fixed on top of the bellows, and the bellows deforms horizontally upon receiving horizontal vibration, is known in the art.
The natural frequency of the vibration isolation table can be greatly reduced with the bellows. If horizontal vibration is transmitted to the bellows from the floor, the bellows deforms horizontally with flexibility to isolate the precision instrument from the horizontal vibration from the floor in an effective manner.
Although an improved vibration isolation table in which the natural vibration frequency thereof in the horizontal direction is further reduced to thereby further improve the performance of the horizontal vibration isolating operation has been desired in recent years, no conventional vibration isolation tables of the aforementioned type can offer satisfactory performance in the horizontal vibration isolating operation.
On the other hand, since the aforementioned bellows cannot return to its original shape by itself after being deformed in a horizontal plane, the precision instrument which is mounted on the mount of the vibration isolation table remains inclined with respect to a horizontal plane if the bellows remains deformed.